1. Field of the Invention
This invention relates generally to mechanical positioning apparatus and, more particularly, to apparatus for simultaneously moving two fixed points which are in spaced relation to each other, in a single direction uniformly toward and away from a reference line perpendicular to the direction of motion.
2. Description of Prior Art
The site of primary interest to me, for utilization of the present invention, is workpiece locating apparatus for presses. For example, in U.S. Pat. No. 3,618,349 issued Nov. 9, 1971 to Gerald V. Roch, and assigned to the assignee of the present invention, there is shown a metal-bending press, more typically known in this country as a press brake, with workpiece locating gauge assemblies behind and in front of the metal forming tools in the press brake. The forming tools are normally elongated, extending in a direction perpendicular to the general direction of insertion of the workpiece into and removal from the press brake, to make various bends in the workpiece.
For some workpieces, the bend must be made along a rather long line from one edge to the other edge of a sheet. In such instances, the sheet is so wide that accurate gauging dictates contact with the sheet at points at least reasonably near the edges of the sheet. This normally requires a considerable horizontal spacing between support points for the gauges themselves. Also, where front gauging is to be used, it is desirable that the machine operating person be able to approach the press between gauge supports such as is possible between the front gauging assemblies 16 and 17 in the above mentioned Roch patent. In these instances, some means must be provided for assuring that the movement of the gauges toward and away from the forming tools for any given bend will be uniform, so that both gauges will stop movement at the same distance from the forming tools. For this purpose, in the pneumatically driven gauges of the above-mentioned Roch patent, a hydraulic master-slave relationship was established to provide the synchronism of movement. A cross shaft, chain and sprocket assembly is employed for synchronism of pneumatic pistons in U.S. Pat. No. 3,824,822 issued July 23, 1974. Some subsequent gauging systems have employed motor-driven screws, rather than pneumatic cylinders, to drive the gauges. In an early, non-motorized gauge for shears, shown in U.S. Pat. No. 1,366,409, issued Jan. 25, 1921, a single handle could be employed to drive two screws, using gearing to drive the gauges or gauge supports in synchronism. Another example of this is present in U.S. Pat. No. 3,115,801 issued Dec. 31, 1963. Another approach has been to employ two motors and screw drives for gauge supports, wherein electronic control means are employed for synchronizing the motor drive, to synchronize the gauge movement and stop positions. This is disclosed in U.S. Pat. No. 4,084,424 issued Apr. 18, 1978 to Gerald V. Roch et al. There has remained a need for synchronizing the movement and positioning of gauge supports, with comparable reliability but with less expense. The present invention is directed to that objective.